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/*
Copyright (c) 2006 - 2008 Volker Krause <vkrause@kde.org>
This library is free software; you can redistribute it and/or modify it
under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with this library; see the file COPYING.LIB. If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA.
*/
#ifndef AKONADI_ATTRIBUTE_H
#define AKONADI_ATTRIBUTE_H
#include "akonadi_export.h"
#include <QtCore/QList>
namespace Akonadi {
/**
* @short Provides interface for custom attributes for Entity.
*
* This class is an interface for custom attributes, that can be stored
* in an entity. Attributes should be meta data, e.g. ACLs, quotas etc.
* that are not part of the entities' data itself.
*
* Note that attributes are per user, i.e. when an attribute is added to
* an entity, it only applies to the current user.
*
* To provide custom attributes, you have to subclass from this interface
* and reimplement the pure virtual methods.
*
* @code
*
* class SecrecyAttribute : public Akonadi::Attribute
* {
* public:
* enum Secrecy
* {
* Public,
* Private,
* Confidential
* };
*
* SecrecyAttribute( Secrecy secrecy = Public )
* : mSecrecy( secrecy )
* {
* }
*
* void setSecrecy( Secrecy secrecy )
* {
* mSecrecy = secrecy;
* }
*
* Secrecy secrecy() const
* {
* return mSecrecy;
* }
*
* virtual QByteArray type() const
* {
* return "secrecy";
* }
*
* virtual Attribute* clone() const
* {
* return new SecrecyAttribute( mSecrecy );
* }
*
* virtual QByteArray serialized() const
* {
* switch ( mSecrecy ) {
* case Public: return "public"; break;
* case Private: return "private"; break;
* case Confidential: return "confidential"; break;
* }
* }
*
* virtual void deserialize( const QByteArray &data )
* {
* if ( data == "public" )
* mSecrecy = Public;
* else if ( data == "private" )
* mSecrecy = Private;
* else if ( data == "confidential" )
* mSecrecy = Confidential;
* }
* }
*
* @endcode
*
* Additionally, you need to register your attribute with Akonadi::AttributeFactory
* for automatic deserialization during retrieving of collecitons or items:
*
* @code
* AttributeFactory::registerAttribute<SecrecyAttribute>();
* @endcode
*
* Third party attributes need to be registered once by each application that uses
* them. So the above snippet needs to be in the resource that adds the attribute,
* and each application that uses the resource. This may be simplified in the future.
*
* The custom attributes can be used in the following way:
*
* @code
*
* Akonadi::Item item( "text/directory" );
* SecrecyAttribute* attr = item.attribute<SecrecyAttribute>( Item::AddIfMissing );
* attr->setSecrecy( SecrecyAttribute::Confidential );
*
* @endcode
*
* and
*
* @code
*
* Akonadi::Item item = ...
*
* if ( item.hasAttribute<SecrecyAttribute>() ) {
* SecrecyAttribute *attr = item.attribute<SecrecyAttribute>();
*
* SecrecyAttribute::Secrecy secrecy = attr->secrecy();
* ...
* }
* @endcode
*
* @author Volker Krause <vkrause@kde.org>
*/
class AKONADI_EXPORT Attribute
{
public:
/**
* Describes a list of attributes.
*/
typedef QList<Attribute*> List;
/**
* Returns the type of the attribute.
*/
virtual QByteArray type() const = 0;
/**
* Destroys this attribute.
*/
virtual ~Attribute();
/**
* Creates a copy of this attribute.
*/
virtual Attribute* clone() const = 0;
/**
* Returns a QByteArray representation of the attribute which will be
* storaged. This can be raw binary data, no encoding needs to be applied.
*/
virtual QByteArray serialized() const = 0;
/**
* Sets the data of this attribute, using the same encoding
* as returned by toByteArray().
*
* @param data The encoded attribute data.
*/
virtual void deserialize( const QByteArray &data ) = 0;
};
}
#endif
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